Manual shift levers are provided with automatic shifting transmissions to permit the operator to have control over selection of the transmission operating condition. For a number of years, these lever assemblies have been incorporated in systems adapted to include an ignition interlock which prevents removal of the shift lever from the park position prior to the operator manipulating the ignition from the lock position, and also preventing return of the ignition to the lock position prior to the transmission being returned to the park position. More recently, these systems have also included brake/transmission shift interlocks (BTSI) which prevent removal of the lever from the park position prior to manipulation of the brake pedal.
The shift lever is detentably retained in the various operating conditions by spring loaded engagement of the detent pawl in selected slots or grooves on the detent plate or gate plate. The detent pawl is generally controlled by an operator actuator, such as a button and rod, to inhibit movement of the lever without prior depression of the button.
Many of the ignition interlocks and BTSI's are designed to operate on the detent pawl and must, therefore, have sufficient system stiffness to withstand the operator input forces exerted thereon prior to the required operator manipulations. This is particularly true of the ignition interlock on floor mounted transmissions which is present primarily to prevent unauthorized movement of the vehicle.